The majority of present day integrated circuits (ICs) are implemented by using a plurality of interconnected field effect transistors (FETs), also called metal oxide semiconductor field effect transistors (MOSFETs or MOS transistors). The ICs are usually formed using both P-channel and N-channel FETs and the IC is then referred to as a complementary MOS or CMOS integrated circuit (IC). There is a continuing trend to incorporate more and more circuitry on a single IC chip. To incorporate the increasing amount of circuitry, the size of each individual device in the circuit and the size and spacing between device elements (the feature size) must decrease.
High dielectric constant materials, also referred to as “high-k dielectrics,” such as hafnium dioxide (HfO2), hafnium silicate oxide nitride (HfSiON), or zirconium dioxide (ZrO2), are considered for the 45 nm node technology and beyond to allow further scaling of gate dielectrics. To prevent Fermi-level pinning, metal gates (MG) with the proper work function are used as gate electrodes on the high-k gate dielectrics. Such metal gate electrodes typically are formed of a metal-comprising material such as lanthanum (La), aluminum (Al), magnesium (Mg), ruthenium (Ru), titanium-based materials such as titanium (Ti) and titanium nitride (TiN), tantalum-based materials such as tantalum (Ta) and tantalum nitride (TaN) or tantalum carbide (Ta2C), or the like. Often, a thin oxide forms on the metal-comprising material when exposed to an ambient environment. The oxide may serve as protection of the metal-comprising material from contamination.
Typically during fabrication of a semiconductor device, a metal-comprising material is exposed to liquid chemistries, such as solvents and/or aqueous solutions, used to remove disposable materials. However, during such exposure, at least a portion of the metal-comprising material also may be removed, resulting in catastrophic effects on the performance of subsequently-formed devices. For example, features, such as metal gates, are formed via photolithography using a patterned photoresist material. The photoresist material is utilized as a mask to define device features, such as gate electrodes, in the metal-comprising material of a semiconductor wafer. After the features are formed, the photoresist is removed from the features. Photoresist typically is removed using a sulfuric acid/hydrogen peroxide mixture (SPM), propylene glycol methyl ether acetate (PGMEA), solvents such as n-methylpyrrolidone (NMP), polyethylene glycol (PEG), and commercial strippers such as AZ400T available from Clariant of Switzerland, or a dry chemistry, such as a plasma. However, these conventional removal methods prove unsatisfactory for the removal of photoresist from metal-comprising material, such as that used to form metal gate electrodes. For example, SPM is an aqueous-based composition with a pH of about 1 and thus results in removal of not only the resist but also at least some of the metal-comprising material and any oxide formed thereon. Removal of any portion of the metal-comprising material and/or its oxide can result in an increase in the threshold voltage (Vt) of a subsequently-formed MOSFET. In addition, wet chemistries often are followed by deionized water rinses that also can remove a portion of the metal-comprising material, thereby adversely affecting Vt. PGMEA and various solvents tend to leave residue particles on the metal-comprising material, which results in high defectivity. Dry chemistries typically do not remove all of the photoresist and, thus, have to be followed by wet chemistry etches, such as with SPM, PGMEA or solvents, that in turn present the same issues set forth above.
Accordingly, it is desirable to provide methods for fabricating a semiconductor device that retain a metal-comprising material when exposed to a liquid chemistry used to remove a disposable material. In addition, it is desirable to provide methods for retaining metal-comprising materials of a semiconductor substrate when exposed to liquid chemistries by using liquid chemistry dispense systems from which oxygen has been removed. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.